How to Control Temperature?

[netrizone]

Thank you very much for the replies! My collection is a mix of large grocery store phals and a couple small ones that are still growing.

The grocery store phals are in thick, 5" ceramic pots. I've stuck a thermometer deep into the soil before, and it was around room temp (10C/50F). This is with the heat mats.

The smaller phals are in 2" plastic pots. When I stuck a thermometer into the roots, I've found that the mats only heat it a couple of degrees warmer.

Because the larger phals are in bloom, I can't cover the entire collection with a sheet or box to trap in the heat. If anyone has any ideas, please let me know!